Bert is a worker in Yanille and is a key figure in The Hand in the Sand quest. After the quest, players can speak to him (or use the right-click option on him) once per day to have him deliver 84 buckets of sand to their bank. He will automatically deliver the sand each day if the player has completed the elite Ardougne Diary, and can be spoken to in order to toggle this on or off if it is not wanted. This effect continues even if the player loses membership.
He can be contacted using the NPC Contact spell in the Lunar spellbook.